code: def testBuildRingGatherPassStructure(self):
      # 1 worker, 1 device
      input_tensors, device_names = self._buildInput(1, 1)
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(1, 1, [0])
      output_tensors = ar._build_ring_gather(
          input_tensors,
          device_names,
          1,
          pred_by_c_d,
          rank_by_c_d,
          math_ops.add,
      )
      self.assertEqual(output_tensors, input_tensors)
      # 1 worker, 4 devices, 2 subchunks
      input_tensors, device_names = self._buildInput(1, 4)
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(
          1, 2, [0, 1, 2, 3]
      )
      output_tensors, pad_len = ar._build_ring_gather(
          input_tensors,
          device_names,
          2,
          pred_by_c_d,
          rank_by_c_d,
          math_ops.add,
      )
      self.assertEqual(0, pad_len)
      # same number outputs as inputs
      self.assertEqual(len(output_tensors), len(input_tensors))
      num_chunks = 2 * len(input_tensors)
      tlen = tensor_shape.dimension_value(input_tensors[0].shape[0])
      for otl in output_tensors:
          self.assertEqual(len(otl), num_chunks)
          for ot in otl:
              self.assertEqual(ot.shape, [tlen // num_chunks])
  
imports: import time
  import numpy
  from tensorflow.core.framework import types_pb2
  from tensorflow.python.distribute.v1 import all_reduce
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import state_ops
  from tensorflow.python.platform import test
  from tensorflow.python.platform import tf_logging
label_desc: Use image node_id 4 for calling the AllReduceTest obj's underlying member method code with example usage: obj.testBuildRingGatherPassStructure() without return types